1. Technical Field
The present invention relates generally to improvements in disk drive systems and in particular to mounting head gimbal assemblies with read/write heads coupled to actuator arms. Still more particularly, the present invention relates to a method of forming a swagable metal arm tip for swagging a head gimbal assembly to a ceramic actuator arm or E-block.
2. Description of the Related Art
An ongoing objective of the disk drive industry is to produce disk drive systems with increasing storage capacity, decreased size, and faster response time. One approach to increasing the storage capacity of a disk drive is to increase the number of disks. However, as the number of disks increases, the height of the disk drive also increases. To maintain the desired size and storage capacity of the disk drive, there is a continuous incentive to reduce the spacing between disks. Additionally, certain applications require low profile (thin) disk drives which, again, demand thin arms and narrow disk spacings. As a limiting design factor, the space between disks must be sufficient to accommodate two read/write heads and two load beam assemblies on which the read/write heads are mounted, and an arm. FIG. 1 illustrates this arrangement of a disk drive 101 having an E-block assembly with multiple actuator arms 113 and with multiple disks 103, each arm 113 having a head gimbal assembly (HGA) 105 made up of one or two load beams 111 and the read/write head 109. The voice coil 107 controls the actuator arms that pivot on the arm hub 115.
While attempting to reduce the spacing between disks, there is also a desire to adjust other properties of the actuator arms such as density, stiffness and damping ability. In order to achieve these properties, there has been a shift to the use of ceramic materials in manufacturing the actuator arms such as that disclosed in U.S. Pat. No. 5,672,435. Alumina and silicon carbide are the simplest and most common ceramic materials used, although other ceramics and composites are also common in the art. The use of these alternative materials for the internal components of hard drives decreases the density while increasing the specific stiffness of those components, leading to performance improvements over traditional drives which employ conventional materials.
While improving the density, stiffness and vibrational qualities of the actuator arms, thus increasing the response time of the arms as they move over the disks, the arms are more brittle and thus more difficult to machine. Machining often results in cracking and chipping of the ceramic arms, as opposed to the use of metal which is more machinable. In particular, machining is often required to form an attachment means for the HGA. Swaging, as one preferred means of HGA attachment to arms, can in turn lead to problems in actuator arm cracking. Welding is another preferred method of HGA attachment, which is possible on metal arms, but is very difficult on ceramic arms. An added problem to present ceramic arms is that the use of alumina and silicon carbide and other ceramic materials that have low electric conductivity results in electrostatic charge buildup which is not easily discharged. Therefore, data destruction due to a build-up and sudden discharge of electrical charges can occur.
While trying to reduce the spacing between disks, there is a desire to also reduce the mass of the actuator and HGA so as to decrease the response time of the disk drive. One way of reducing the mass of the head HGA is to bring the actuator pivot 115 closer to the center of the disk stack 117, as shown in FIGS. 1 and 2. Reducing the disk diameter results in shorter, and thus lighter, lower inertia HGAs and arms. The preferred way to achieve the smallest possible spacing between the actuator pivot center and the center of the disk stack is for the actuator arms 113 to fit between the disks 103 as shown in FIG. 2. Therefore, the space between disks must be sufficient to accommodate not only two read/write heads 109 and two load beams 111, but also an actuator arm 113 and the attachment means for attaching the HGA assembly to the arm.
Some prior art disk drives attempt to reduce the number of components between disks by attaching the load beams directly to the actuator arms, as, for example, by welding the load beams to the arms. Since metal HGAs can not be directly welded to ceramic arms, another method of attaching HGAs to the arms by means of swaging techniques must be used. Prior art swaging techniques involved swaging a spud, or boss, made of a hard material into an actuator arm made of a soft material. During the prior art swage process, an oversize, hard ball enlarges the spud cylinder into the inside surface of the actuator arm hole, causing the outside surface of the spud cylinder to xe2x80x9cbitexe2x80x9d into the inside surface of the actuator arm hole. However, with the use of hard, brittle ceramic material, the current swaging techniques will not xe2x80x9cbitexe2x80x9d into the actuator arm and can cause the actuator arm hole to fracture.
It is therefore one object of the present invention to provide a means to attach a head-gimbal-assembly to a ceramic or metal matrix composite actuator arm.
It is another object of the present invention to provide an actuator that has low inertia to reduce seek times and high stiffness to increase both servo bandwidth and shock resistance.
It is another object of the present invention to provide a means to weld a metal suspension to a ceramic arm.
It is another object of the present invention to provide a means to remove and reattach HGA""s from a ceramic arm.
It is yet another object of the present invention to provide a conductive metal outer surface to the ceramic arm.
The preferred aspect of the invention is a swagable ceramic actuator arm that is formed by placing a metal insert into a hole in the actuator arm and forming or adhering the metal insert within the hole, the adhered or formed metal insert thus constituting a metal swage plug that can then be machined further. The foregoing are achieved as is now described. A swagable metal actuator arm tip having a metal swage plug for ceramic actuator arms is made by first providing at least one actuator arm formed from a ceramic material and having a tip opening, the tip opening having an inner edge of a defined thickness. Next, a metal insert is formed or adhered within the tip opening having a thickness that is substantially similar to the thickness of the inner edge, the metal insert also having an outer edge that makes cohesive contact with the inner edge of the tip opening. Third, a swage annulus is formed within the metal insert, the swage annulus having a predetermined inner swaging diameter, the predetermined inner swagging diameter being sized to accept a swage ball coupling of a tip gimbal assembly, whereby the metal insert provides a means of attaching the head gimbal assembly to the actuator arm. There are six basic methods by which the metal insert can be formed or adhered into the tip opening to form the metal swage plug: cold forming, die casting, pressure infusion casting, forging, thixoforming, or the use of adhesives.
The above as well as additional objectives, features, and advantages of the present invention will become apparent in the following detailed written description.